Viruses are the smallest pathogenic microorganism, and viral infectious diseases have been one of the major diseases threatening human health, which are characterized by high incidence, fast spread, wide epidemic and great variability. Flaviviridae comprises three virus genera, which are Flavivirus, Pestivirus and Hepacivirus, and include over 60 viruses in total.
Dengue fever virus (DV) belongs to positive strand RNA virus of Flavivirus of Flaviviridae, and has 4 serotypes. Classical dengue fever (DF) and Dengue henorrhagic fever/Dengue Shock Syndrome (DHF/DSS) caused by mosquito-borne transmission are acute infectious diseases, the pathogen thereof may cause a number of diseases in humans, resulting in death in severe cases. Such diseases are widely distributed, and DF cases are greatly increasing recently. Such fatal infectious diseases have threatened the health of one third of the global population, and have become the important public health problems in Southeast Asia, Pacific islands, Caribbean and Central and South America.
At present, there have been no effective vaccines to prevent Dengue fever and no specific antiviral drugs to effectively treat Dengue fever in the world. Because of the particularity of diseases caused by DV, i.e., the antibody dependent enhancement and viral evolutionary mutation of DV infection, the research on DV vaccines has not made a significant breakthrough for many years.
Hepatitis C virus (HCV) belongs to Hepacivirus of Flaviviridae, and is a single-strand positive strand RNA virus with spherical viral particle. In 1989, Hepatitis C virus was identified as pathogene HCV for transfusion-associated non-A, non-B hepatitis, which may cause many clinical symptoms, most of them are benign or subacute ones. Symptom of chronic hepatic injury for many patients may not appear until 10-30 years after infected.
Researches on related drugs are blocked due to lack of proper experiment systems and animal models. So far, there is no vaccine or treatment method which can be used to treat Hepatitis C virus of all subtypes.
Under such circumstances, it is particularly important to develop drugs against Flaviviridae viruses, particularly Dengue fever virus and Hepatitis C virus, with low toxicity, high effectiveness and low price.